The development of geodesy and cartography have led to the further development of various systems for defining the location of specific points on the surface of the earth or on a representative map or chart. Two primary principles of point location have been developed: The polar coordinate system (e.g., degrees of latitude and longitude) and the Cartesian coordinate system of ordinates about a set of orthogonal axes.
Of the two, the Cartesian coordinate system is preferred for use with flat surfaces such as conventional maps and charts. The problem with the polar coordinate system is that it is based upon an angular measurement; hence, absolute distances increase with the distance from the origin. The inherent problems associated with this system are apparent on larger scale maps and charts.
As a result, most makers of maps and charts for the layman nave used a Cartesian coordinate or "grid" system to specify locations on the map. The various systems developed are arbitrary at best, and provide no clear transfer from one map to specify another, particularly in the case of maps or charts made by different companies. The most commonly used system is an alphanumeric one, in which a series of numbers are used to define points along one axis and a series of alphabetical letters are used to define points along a second perpendicular axis. While this system is superior to the polar coordinate system for use with maps representing a relatively small area of the surface of the earth (e.g., a single state road map or the like), the alphanumeric notation used provides no rapid and clear concept of the location of a point on that map. A designation such as "M-13" is, of no value to a person, unless that person also knows the limits of the notation scales used. In the above example, an area within a grid column "M" may be on the centerline of the defined map, if the entire alphabet is used. On the other hand, if only the first half of the alphabet is used, then the area will lie somewhere very near one edge. In addition, such conventional systems describe only a general area, rather than pinpointing a specific location as in the case of the present invention. Thus, a user of such a conventional system would be forced to search a relatively large rectangular area of a map in order to find a point identified as being located in (for example) area "M-13." In fact, it is likely that a plurality of point" of interest will be located in such a single rectangular area, with each point of interest having the same general location description even though they may be widely separated. This can lead to less than optimum choices in routes and other logistic decisions if planning is based upon a callout for a single general area containing several widely spaced points.
Such alphanumeric systems are limited in another respect, and that is that at least along the axis using letters of the alphabet, no more resolution than that provided by the 26 characters of the alphabet may be provided. If resolution to 100 units is desired, some additional system must be added. Other deficiencies are apparent with these commonly used reference systems, which render such systems cumbersome and confusing to the user.
The need arises for a coordinate system for use with maps, charts and the like, which system is easily understandable by the user and which is easily transferable between various maps and scales. The system must also easily accommodate the location of points in a three dimensional volume. Due to the ease of use of such a system, the teaching of the system to others and visualization of locations would also be readily achieved.